The resultant force on the suspended ball

A. In the process from A to B, constant force F does work, which increases the kinetic energy and gravitational potential energy of the ball. Therefore, according to the functional relationship, constant force F does work more than the increment of spherical potential energy, so A is wrong;

B, the constant force is not zero, and the direction of the ball is consistent with the direction of the force, so the work done by the constant force on the ball is not zero, so B is wrong;

C, the tension of the thin thread is always perpendicular to the speed direction, so no work is done. Therefore, C is correct;

D, if the force F is removed at point B, because of the speed, the maximum angle of deviation from the vertical direction when the ball swings back and forth is greater than θ, so D is correct;

So: CD.